1. Intraspecific trophic variability has important ecological and evolutionary implications, and is driven by multiple interacting factors. Functional traits and environmental conditions are important in mediating the trophic niche of individuals because they determine their ability to consume certain prey, their energetic requirements, and resource availability. In this study, we aimed at investigating the interacting effects of functional traits and environmental conditions on several attributes of trophic niche in natural populations.
2. Here, we quantified intraspecific variability in the trophic niche of 12 riverine populations of European minnow (Phoxinus phoxinus) using stable isotope analyses. Functional traits (i.e. morpho‐anatomical traits) and environmental conditions (i.e. upstream–downstream gradient, forest cover) were quantified to identify the determinants of (1) trophic position and resource origin, (2) trophic niche size, and (3) trophic differentiation (β‐diversity) among populations.
3. We demonstrated that trophic position and resource origin covaried with functional traits related to body size and locomotion performance, and that the strength and shape of these relationships varied according to local environmental conditions. The trophic niche size also differed among populations, although no determinant was identified. Finally, trophic β‐diversity was correlated to environmental differentiation among sites.
4. Overall, the determinants of intraspecific variability in trophic niche appeared highly context‐dependent, and related to the interactions between functional traits and environmental conditions. Because populations are currently facing important environmental changes, understanding this context‐dependency is important for predicting food web structure and ecosystem dynamics in a changing world.

中文翻译：

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将营养位和功能位的种内变异性沿着环境梯度联系起来

1. 种内营养变异性具有重要的生态和进化意义，并受多种相互作用因素的驱动。功能特质和环境条件对于调解个人的营养利基至关重要，因为它们决定了他们消耗某些猎物的能力，精力充沛的需求和资源的可用性。在这项研究中，我们旨在调查功能性状和环境条件对自然种群中营养生态位的几个属性的相互作用。
2. 在这里，我们使用稳定同位素分析对欧洲min鱼（Phoxinus phoxinus）的12个河流种群的营养生态位中的种内变异进行了定量分析。对功能性状（即形态解剖特征）和环境条件（即上下游梯度，森林覆盖）进行了定量分析，以确定以下因素的决定因素：（1）营养位置和资源来源，（2）营养位的大小和（3）营养的人群之间的差异（β-多样性）。
3. 我们证明了营养位置和资源起源与与体型和运动表现有关的功能性状共变，并且这些关系的强度和形状根据当地环境条件而变化。营养种群的生态位大小也有所不同，尽管未确定任何决定因素。最后，营养β-多样性与站点之间的环境差异相关。
4. 总体而言，营养生态位中种内变异性的决定因素表现出高度的背景依赖性，并且与功能性状与环境条件之间的相互作用有关。由于人们当前正面临着重要的环境变化，因此了解这种环境依赖性对于预测变化中的世界的食物网结构和生态系统动态非常重要。